Pingopongo
Cadet
- Joined
- Jan 6, 2010
- Messages
- 6
Hi guys I was wondering if someone could put me in the right direction as to what could be the problem with a Mercury 25 hp 2 stroke outboard motor.
Now before I start I'm mechanically minded and I'm a Auto Electrician by trade.
I purchased this 1985 outboard from eBay a while back and they said that it was in good running condition ( Yeah right ). Upon starting it does idle but shakes excessively like missing a cylinder. When I rev it up it stutters and then evens out but revs go really high ( checked both spark outputs and both cylinders are firing). Compression was cylinder 1 =150psi and cylinder 2 = 175psi, upon strip down of motor I found carbon blockage of exhaust relief holes causing high compression on that cylinder. After cleanup of engine and new gasket kits fitted I also fitted some racing reeds that I got cheap.
Now my first instict was that it had carb issues so I ordered and fitted a new repair kit for the tillotson carb type Bc1b. Now with it all back together and running, same problem is still there. Compression on each cylinder is now 150psi exactly. Engine shakes and as you rev it up it splutters then revs it's guts out. I'm running engine with prop in nuetral and ear muffs for water cooling.
Would it be that it needs prop to be running for load? As I'm not familiar with these types of engines ( give me a complexed EFI system any day ) . I also have a similar engine 15hp Merc 2 stroke which runs perfectly no shaking and smooth idle. Any ideas? Regards Dino
Now before I start I'm mechanically minded and I'm a Auto Electrician by trade.
I purchased this 1985 outboard from eBay a while back and they said that it was in good running condition ( Yeah right ). Upon starting it does idle but shakes excessively like missing a cylinder. When I rev it up it stutters and then evens out but revs go really high ( checked both spark outputs and both cylinders are firing). Compression was cylinder 1 =150psi and cylinder 2 = 175psi, upon strip down of motor I found carbon blockage of exhaust relief holes causing high compression on that cylinder. After cleanup of engine and new gasket kits fitted I also fitted some racing reeds that I got cheap.
Now my first instict was that it had carb issues so I ordered and fitted a new repair kit for the tillotson carb type Bc1b. Now with it all back together and running, same problem is still there. Compression on each cylinder is now 150psi exactly. Engine shakes and as you rev it up it splutters then revs it's guts out. I'm running engine with prop in nuetral and ear muffs for water cooling.
Would it be that it needs prop to be running for load? As I'm not familiar with these types of engines ( give me a complexed EFI system any day ) . I also have a similar engine 15hp Merc 2 stroke which runs perfectly no shaking and smooth idle. Any ideas? Regards Dino